To control dobbies, pattern cards with nonperforated or perforated portions are used which are read by needles of a control mechanism. The movement of the reading needle toward the pattern card is done with the aid of gravity or in fast-running machines with pretensioned springs or special drive parts. Upon increasing the operating speed, the time which is available for reading is reduced. The reading needles are moved forwardly faster and hit with greater speed the nonperforated parts, and in time can result in fatique distortions in the pattern card, for example deformations and breakage of the nonperforated parts and eventually cause control errors.
By reinforcing the pattern card, a stiffening thereof would result and would make same heavier and bulky. The needle mass can be reduced only in as much as the durability of the needle is not affected. A direct and purposeful control of the movement of the needle leads to time losses during the course of the control operation and also causes vibrations in the needle.
The purpose of the invention is a simple structure of a reading device for a dobby which permits an increase in the operating speed thereof.
This is inventively achieved in a reading arrangement of the abovementioned type by providing an element which yields in axial direction of the reading needle and is arranged either on the reading needle or on the pattern card.
With this arrangement, the nonresilient mass portion of the reading needle which directly engages the card can be reduced by reducing the respective needle length to the movement requirements into the pattern card. The needle portion which is necessary for transmitting the reading result is movably connected in axial direction to a base part. The yielding effect can be assured by an elastic deformation or by relative movement against a frictional resistance and the latter can be applied as an additional arrangement parallel to the first one. It is important that the entire needle length is reduced when the needle strikes a nonperforated portion of the pattern card and that prior to the next following reading of the pattern card and during an indexing of the pattern card the original length is again achieved.